Bigtreetech S42B Closed-Loop Driver Controller

Most people, when upgrading driver control boards go with TMC2208s or TMC2209s. I decided to go with the Bigtreetech’s closed-loop drivers. These are a bit more involved, but worth it, IMO, once you get them working correctly.

And there’s my issue. The two boards (they’re on the X and Y axes) calibrate and run in open-loop mode, but will not work in closed-loop mode. I’m hoping someone here might have some insight into this issue.

About my machine… It’s an Anycubic Mega S. And, I have been having a time getting the drivers to work. It might have been easier, and faster, if I’d have purchased the boards with motors already attached. Instead, I purchased the kits, which you install as a DIY kit.

If you’re considering upgrading to these, things you should know before hand - the DIY kit requires you to attach a magnet to the rear shaft of each motor. This can be difficult. Some motors don’t seem to be compatible with the kits. The harness from the board to your motor may not match, so you may need to correct that. It was difficult to find the motor breakout’s pin out. What I finally found was that it’s labeled as ABCD, or 1A/1B/2A/2B. The harness had BC swapped. Fire my machine, I had to make it straight through. Until I found this info, I couldn’t even get them to calibrate.

You also may have to make a few changes to the firmware. Teach Tech has a good video on this - S42B closed loop stepper motors - No more layer shifts! - YouTube

At this point, I’ve gotten the X and Y Axes working but am coming to the conclusion that it may not be possible to set up the Z-axis due to the way anycubic designed the Mega series, which is one controller output from the motherboard to a splitter. So, I may end up placing a TMC2209 on their spot to smooth it out. Not that it’s needed, but I have one available from when I upgraded my laser etching machine.

Thanks for the warning. I shall go no way near this machine.